CC1125: CC1125+SE2435L design

Part Number: CC1125
Other Parts Discussed in Thread: CC1190, , CC1120, BOOSTXL-CC1120-90

Hello Everyone,

After using for a really long time CC1125 + CC1190 I found myself in the situation that i have to change to SE2435L front end due to the chip shortage.

We have been using the Ti proposed solution of 1 line for TX/RX for CC1125/CC1190 until now but i would like to know the advantages of splitting the RX and RX path as for example this document shows.

https://www.renesas.com/document/apn/rl78g1h-raa604s00-board-design-guidelines-improving-communication-link-budget-rev100?language=en&r=1245211

Also i would like to know which programs could be used to simulate filters and attenuation(Lt spice maybe)?

Kind regards Javier.

  • Hi Javier,

    Please could I double-check I understand your first question - are you looking to replace the CC1190 with the SE2435L due to chip shortage but keeping the CC1125 transceiver?

    Regarding CAD tools, are you looking for free software or can you purchase software?

    Regards,
    Zack

  • Yes, this is exactly what we are forced to do (CC1125+SE2435L) due to extremely high prices our providers are asking for this chip.

    For CAD we are already using altium, but i was referring to simulation.

  • Thanks for clarifying.

    The main advantage is flexibility in the matching networks for TX/RX; if they are separate it is possible to optimise for each path (if you need to make any changes at some point) at the expense of board space, extra components, and design effort. The operation of the specific front-end you are using will influence this as well, of course.

    Is there a design of a specific split TX/RX path in the linked document that you were looking at? Which TI reference design are you referring to where there is one line for TX/RX? The CC1125-CC1190 designs I am aware of use seperate matching networks between the CC1125-CC1190 TX/RX paths.


    For simulation, we recommend software such as Advanced Design System (ADS) or Microwave Office. You can then simulate the effects of the PCB layout and components (such as using Murata's component libraries) when considering the impedance matching of the device(s). This is especially important if your design differs from TI's reference designs.

    You can calculate PCB trace impedances using TX-Line Transmission Line Calculator (free): www.cadence.com/.../awr-tx-line.html

  • Thank you, the design we are using is legacy from CC1120+CC1190 ,the reference design used was BOOSTXL-CC1120-90 which used the integrated pasive but based on Design Note DN039 the results show better link budget with discrete wirewound  inductors.

    thats the route we took, and based in what you tell me and what I'm seeing I will try to keep changes to a minimum, that means keeping the one line design.

    I understand that if after the SAW filter (example for 915: https://www.mouser.es/datasheet/2/842/rfgm_s_a0010761759_1-2295301.pdf)  is matched for 50 ohm the TR port can be connected directly?

  • To avoid confusion: internally, the IPC has separate matching for the TX/RX paths but the advantage is of course that you only have to work with single input/outputs matched to 50 Ohms. The advantage of using wire-wound inductors is discussed in Section 5 of SWRA168A (DN017 -- CC11xx 868/915 MHz RF Matching (Rev. A)): https://www.ti.com/lit/an/swra168a/swra168a.pdf and also in this E2E thread: e2e.ti.com/.../what-l-is-better-in-rx-matching-wirewound-or-multilayer
    The IPC cannot use these, hence its performance is not quite as good as the discrete reference design. However, it has other advantages as discussed in the IPC App Notes like the one you linked.

    So, just to clarify, the difference is not due to having one or separate TX/RX paths, as all of the designs actually have separate matching for the TX/RX paths. The difference is in the type of matching components used and the flexibility, cost, effort, and board space you find acceptable for your design. The IPC reduces the effort you have to spend on matching but at the expense of some performance.

    The SE2435L states that it is matched to 50 Ohms on its input/output ports, so you should be able to directly connect it to the TR port if the SAW filter output is also matched to 50 Ohms.

  • thank you , this is what i was looking for.